Contact lens



Nov.'25,1941. H. 1.. HUNTER 2 ,2s4;o's o CONTACT LENS Filed July 28,1939 2 Sheets-Sheet l I Imfen t? ttorn e y.

Nov. 25, 1941.

H. L. HUNTER coumcw LENS Filed July 28, 1939 2 Sheets.. .2

nd/ en on llllllilil Patented Nov. 25,1941

,UNITED STATES PATENT OFFICE.

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tact lenses and more particularly tofitted annularly curvilinearCODOSVO-OODVQX lenses.

.Known methods of manufacturing concaveconvex contact lenses are; byblowing, by grinding pressed blanks or, by molding and then grinding thecorneal part. Another known type of contact lens is formed with aplastic sclerotic part and a glass corneal part. Blown lenses, althoughpolished, are not always uniform in thickness and, when visualcorrection is indicated, a spot is formed on the exterior surface of thecorneal part.

In each of the above noted types of lenses, the

interior surface of the, concave-convex corneal part is semi-sphericaland in all except the molded type. the interior surface of the scleroticpart,

is formed semi-spherical. Obviously, concavoconvex lenses formedsemi-spherical do not properly fit all patients because only a very fewhave semi-spherical eyeballs. In the majority of cases, the eyeballs areirregular or astigmatic (annularly curvilinear). In the irregular orastigmatic sclera case, a semi-spherical lens tends to rock on the partof the flattest meridianleaving clearance at the part where the meridiancurvature is thegreatest. Asa result, the lens frequently becomesmisplaced.

In such an event the corneal sclera junction or contact the eyeball tothe discomfort of the patient. If the contact pressure is sumcient, the

blood vessels are impinged or their normal functioning is impaired. Animproperly fitted lens does not correct retinal or lentic'ularastigmatism or prismatic defects.

It is therefore, an object of the invention to provide a concave-convexlens ground along continuous plotted curves to fit an irregular orastigmatic sclera and" correct retinal andlentlcular astigmatism andprismatic defects.

Another object is to provide a contact lens with annularly curvilinearooncavo-convex corneal and sclerotic parts to'insure an accuratephysical and optical fit.

Another object is to provide a method where-' bya contact lens may beground curvilinear annularly and meridionally.

The foregoing and such other objects of the invention as will becomemore apparent hereinafter, will be more readily understood from aperusal of the following specification, lnwhich reference is made to theaccompanying drawings, wherein: I

limbus, as well .as the corneal part, frequently Fig. 1 is a centralsectional view of a curvilinear contact lens.

2 is an inside bodying the invention.

Fig. 3 is a diagram'of the plotted meridional contour.

Fig. 4 is a schematic view illustrating the proiection of a silhouetteofthe cast.

Fig. 51s a plan view of a matrix.

Fig. 6 is an elevational view of a grinding machine. showing parts insection.

In fitting a lens to a patient, a semi-spherical or toric trial lens isusedin determining the refraction and visual acuity. The'findings arerecorded to aid in making a fitted contact lens l of the correct power.

Then a mold, preferably consisting of anelastic substance known to thetrade as negocoll, is made of the eyeball. Next, a plaster cast it ismade from the mold and subsequently altered to provide for the essentialcorneal and limbus clearances and the previously dete min d refractionand visual acuity or correcting power. a

A matrix II is made after the altered cast has set and hardened. It maybe made of any suitable material, such'as for example, cast stone, lowfusion metal, plaster electroplated, or any suitable plastic rosincompound. The. matrix may be formed directly on the cast: that is, fullsize, or should an enlarged matrix be desired, the cast is positionedbefore an opaque projector l I and intermittently repositioned so as toproject a silhouette of each of a plurality of meridional contours ontoa .calibrated chart It. A record Moi the charted contours is'made in amanner hereinafterdescribed, and subsequently used to build up anaccurate matrix than the cast.

The matrix 18, either-full'size or enlarged, is then placed on agrlndingmachine 2|, the details of which constitute no part of the presentinvention, to serve as a guide for its grinder element 22. A pressedglass lens blank Ii, is then placed in said machine and ground on onesurface. The grinder element is guided thereover by the irregularcontour of the matrix. Another matrixis made for use to guide thegrinder elenient over the other surface of the lens, allowance beingmade, in said second matrix. .for the required correctional power ascalculated from theuseof thetrlal lens.

Obviously, the finished lens conforms to and 1 snugly embraces thesclerotic contour of the eyeball, irrespectiveof whether or not thesclera plan view of thelens an.

considerably larger is semi-spherical, irregular or astlgmatic, and

embodies the required correctional power and the necessary clearancesover the cornea and limbus to avoid contact therewith.

It is apparent that the lens, ground to conform to an irregular orastigmatic' sclera and to include the required correctional power, isground on irregular curves. In other words, at least its interior orconcave surface is curvilinear annularly and meridionally. The exactcontour of each meridional curve need not be individually determined orcalibrated in the event that a matrix of full size is to be used, butthe calibration readings obtained from the projection chart I9 andrecorded for use in making the enlarged matrix should be retained forfuture lens replacement. The calibration of each meridional contour isaccurately identified with reference to the corresponding meridian'ofthe eyeball by suitably marking the meridians (as illustrated by dotdashlines m on lens I j of Fig. 2 and matrix It of Fig. and projecting thesilhouetteof the .cast, at these meridians only, upon the chart.

Obviously, more meridians than those illustrated I may be employed.

- Fig.3 illustrates the plotting of one meridional contour to correspondto the contour of a meridional silhouette it of the cast l5. As shown,two sets of uniformly spaced radial lines 1' are used to plot thecorneal and the sclerotic meridional curves. Each radial line 1' ismarked at a point l2 corresponding to the length of a corresponding lineon the silhouette chart H. For example,

the radial line 1" may measure 12.5 mm. from its terminal T to its pointl2. The point II on the next'line 1'" may measure 12.55 mm. from saidterminal, the next point 12.00 mm. from said terminal, .etc. Thismeasuring and marking continues until all contour points l2 on both setsof radial lines 1' are recorded. The curve C is then plotted to passthrough each point l2 and is an exact reproduction of the contour of thesilhouette. This curve is used to form the proper meridional contour ofthe matrix It.

Measuring and plotting is repeated until each contour, obtained byprojecting different meridional silhouettes of the cast, is reproducedand subsequently reconstructed in the enlarged matrix.

' Obviously, the interior and exterior surfaces of the matrix are notsemi-spherical but are curvilinear both annularly and meridionally dueto an exact reproduction of the eyeball contour as modified to providefor the required clearances and correctional power.

- While grinding the interior or concave surface, the area formed by theshortest radius is ground first and its longer radii later, whereaswhile grinding the exterior or convex surface, the area formed by thelongest radius is ground first and the shortest radii later.

Inasmuch as the various areas A, B, etc., are each'exceedingly small andeach includes portions of plotted curves defining an irregular parabola,no line of demarkation is present at the juncture of adjacent areas.

Although a cast preferably is made.i'1om a mold of the eyeball, ashereinbefore described, it should be obvious that should the eyeball bebut slightly curvilinear, the necessary matrix can be constructed withreasonable accuracy from the calculations and observations.obtainedduring use of the trial lens.

It should .be understood; that, while the meridional lines m areillustrated in, association with the lens, said lines do not appear.thereon but are marked upon the cast prior to making the matrix; that,the disclosure as a whole is illustrative only and not restrictive and;that, the invention embodies such variations in detail and procedure asmay readily fall within the spirit of the invention and the scope of theappended claims. v

Iclaim:

1. The method of producing a one piece concave-convex lens whichconsists of making a negative mold of the contour of an eyeball overwhich the finished lens is to vbe fitted, making a positive cast fromsaid mold, modifying the contour of said cast to include necessarycorneal and limbus clearances and any indicated correctional power,marking agplurality of meridionallines on said cast, placing saidmodified cast before a projector and projecting a silhouette of itscontour along one of its meridians onto a callthe many plotted curvesconstituting, its various meridional and annular contours.

A lens ll ground to conformto such a matrix is physically and opticallycorrect as distin guished, for example, from a blown lens which,although blownto conform to a mold, is effected by shrinkage andpolishing. Such shrinkage and subsequent polishing clearly changes thelens contour, perhaps but slightly. Since the difference between anaccurate fit and a miss-fit is extremely minute, such a lens frequentlyis highly objectionable.

As illustrated in Figs. 1 and 2, both the interior and the exteriorsurfaces l3 and I4 respectively, of the improved lens H are curvilinear;

both annularly and meridionally. In the lens adjacent thereto.Similarly, the curvatures of the various adjacent areas in alldirections may vary according to the exact annular and merid ionalcurvilinear contour of the matrix which is 75.

illustrated, the curvature of the area A defined brated chart, recordingthe readings obtained from said chart, successively repositioning saidcast before said projector and projecting silhouettes of its contoursalong other meridians onto said chart, recording the readings obtainedthereby, plotting a curve of each'silhouette, making a negative matrixembodying the contours of said-plotted curves, and finally placing saidmatrix in a grinding machine to guide its grinder over the surface of alens blank.

2. The method of producing a concavo-convex lens which consists ofmaking a negative mold of the contour of an eyeball over which thefinished lens is to be fitted, making a positive cast from said mold,modifying the contour of said cast I to include necessary corneal andlimbus clearances and any indicated correctional power,-

-marking a plurality of meridional lines on said .said chart,successively repositioning said cast before said projector andprojecting silhouettes of its contours along other meridians onto saidchart, plotting a curve of each silhouette, mak

ing a negative matrix embodying the contours of said plotted curves, andfinally placing said matrix in a grinding machine to guide its grinderover thev surface of a lens blank.

3. The method of producing a contact lens having a curvilinear surfacedefined by a plua calibrated chart, plotting a curve-based upon thereadings obtained from said chart, succesof its contour along one of itsmeridians onto sively repositioning said cast before said pro.- jectorand projecting silhouettes 01 the contours of its other meridians ontosaid chart, plotting a curve of each of said silhouettes, making anegative matrix embodying said plotted curves, and finally placing saidmatrix in a grinding machine to guide its grinder over the surface of alens blank.

HUGH L. HUNTER.

